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8D11PCH2 Offline
#21 Posted : Wednesday, 6 January 2021 1:42:47 PM(UTC)
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Originally Posted by: Smitty2 Go to Quoted Post
Originally Posted by: 8D11PCH2 Go to Quoted Post
Originally Posted by: Smitty2 Go to Quoted Post


But.. and this is where things started to unwind, Milamunda Racing (aka HDT racing team) decided they would use the large valve heads and better inlet manifold from the road cars on VC race cars
(VB racers used SMALL valve heads as CAMS had outlawed L34 style engines as used on A9X) as they were getting a pasting from Johnson and other Falcon competitors



I cannot see where the CAMS had outlawed L34 engines. The L34 spec engine was only homologated for use in the LH/LX Torana not a VB Commodore.
It was simply a failure on the part of GMH for not homologating a VB or VC model with a 308 with big valve heads and other useful performance mods.



that is incorrect.....
CAMS outlawed the big valve L34 engine ....as it also did re rear disk brakes on Toranas (I kid you not) when the Commodore was presented as the car to replace the A9X
(and at the same time the XD taxi for the XC Coupes) complete set of NEW rules...

any reading of the history of tin top racing in Australia gives full and better details of this




As far as I can see the Group C rules did not change all that much between 1979 and 1980. If anything the changes that were made allowed more freedoms with the engines than the 1979 rules did.
This outlawing of L34 engines and disc rear brakes on A9X must have been the subject of an amendment to the 1980 CAMS Manual of Motorsport? as the Manual, as originally printed, does not state anything that would lead one to believe the A9X could not have raced in 1980 with the exact same specs as it did in 1979.

I will consult a friend of mine on the subject as he would know better than any of us what the CAMS did and their reasons.

HK1837 Offline
#22 Posted : Wednesday, 6 January 2021 1:55:57 PM(UTC)
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I thought they banned the A9X homologation, and forced the cars to be run as SS hatchbacks hence the smaller valve engine, rear drums and no rear spoiler or bonnet scoop. Not sure if this affected sedans though? The smart thing to do would be to have run an L34 again, so kept the L34 engine but got to have the T10 and 10-bolt plus rear spoiler.
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8D11PCH2 Offline
#23 Posted : Wednesday, 6 January 2021 2:28:07 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
I thought they banned the A9X homologation, and forced the cars to be run as SS hatchbacks hence the smaller valve engine, rear drums and no rear spoiler or bonnet scoop. Not sure if this affected sedans though? The smart thing to do would be to have run an L34 again, so kept the L34 engine but got to have the T10 and 10-bolt plus rear spoiler.


That sounds more plausible. As A9X was an evolution you had to use the full evolution or none of it. You couldn't pick and choose which bits of an evolution you wanted and the bits you didn't.

Grice's Hatchback in 1980 did however have the wheel arch flairs did it not?
HK1837 Offline
#24 Posted : Wednesday, 6 January 2021 2:35:09 PM(UTC)
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Yes, and it had a 10 bolt and T10 as well afaik. I had axles in my LX hatchback Salisbury that came out of that 1980 car.
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8D11PCH2 Offline
#25 Posted : Wednesday, 6 January 2021 2:43:08 PM(UTC)
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Found this on Wikipedia but I'm not convinced this is the truth.

The ATCC had expanded to 11 rounds in 1976 and 1977, but the 'Golden Era' often had a thin veneer as uncompetitive small engined cars bolstered entries for many years. The low point saw just nine cars competing for the opening round at Symmons Plains in 1980, though this could be attributed to new CAMS engine emission rules which effectively banned the 1979 Holden Torana hatchback's and Ford Falcons.

In 1980 Group C, under engine modifications, it states that emission control equipment may be removed or rendered inoperable.
So I don't know how that would ban something like an L34 spec engine that didn't have much in the way of emission control equipment to start with.

Edited by user Wednesday, 6 January 2021 2:44:38 PM(UTC)  | Reason: Not specified

HK1837 Offline
#26 Posted : Wednesday, 6 January 2021 3:41:53 PM(UTC)
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I think that is someone putting 2 and 2 together and getting 5.5. I think it means the original 1973-4 engines that were allowed to carry through to 1979 were no longer allowed. So the manufacturers had to use engine components as fitted to the later 70’s production cars. The avenue to get international FIA homologated engines into GroupC must have been used to get a high power 350 into the Z28’s and also the hipo Celica engines amongst others.
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Dr Terry Offline
#27 Posted : Wednesday, 6 January 2021 7:55:41 PM(UTC)
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This is my point about confusing rules in 1980. I can fully understand the thing about not allowing pre-ADR27A Cleveland 4V GT engines & the L34 equivalent in XCs & LXs.

But why couldn't they race A9Xs as is. i.e; small valve heads but with the factory rear axle, flares & rear disc brakes ?

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8D11PCH2 Offline
#28 Posted : Wednesday, 6 January 2021 9:15:38 PM(UTC)
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Think I may have found the confusing rule change for the valves.

1979: Valves must be of the original dimensions.

1980: Valves must be of the the same head diameter and seat angle as the standard component.
Dr Terry Offline
#29 Posted : Thursday, 7 January 2021 5:53:38 AM(UTC)
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Originally Posted by: 8D11PCH2 Go to Quoted Post
Think I may have found the confusing rule change for the valves.

1979: Valves must be of the original dimensions.

1980: Valves must be of the the same head diameter and seat angle as the standard component.


As I said, I can fully understand the small valve thing, this is how the A9X came, but why couldn't they run the rear discs, when they were std equipment for all A9Xs ?

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8D11PCH2 Offline
#30 Posted : Thursday, 7 January 2021 6:50:37 AM(UTC)
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Originally Posted by: Dr Terry Go to Quoted Post
Originally Posted by: 8D11PCH2 Go to Quoted Post
Think I may have found the confusing rule change for the valves.

1979: Valves must be of the original dimensions.

1980: Valves must be of the the same head diameter and seat angle as the standard component.


As I said, I can fully understand the small valve thing, this is how the A9X came, but why couldn't they run the rear discs, when they were std equipment for all A9Xs ?

Dr Terry


Am unable to find any differences in the 1979 and 1980 Group C rules that would explain why the A9X Torana could not run rear discs, rear spoiler and bonnet scoop in 1980.
Dr Terry Offline
#31 Posted : Thursday, 7 January 2021 7:14:08 AM(UTC)
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Originally Posted by: 8D11PCH2 Go to Quoted Post
I Am unable to find any differences in the 1979 and 1980 Group C rules that would explain why the A9X Torana could not run rear discs, rear spoiler and bonnet scoop in 1980.


My point precisely. Who was running CAMS in those days, Gilbert or Sullivan ?

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castellan Offline
#32 Posted : Thursday, 7 January 2021 9:50:13 AM(UTC)
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Originally Posted by: 8D11PCH2 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post


Look at the VB race engine, I have 331hp and the blue VC is 391hp AT 6500RPM with L34 valves and 10.5:1 compression ? how with stock pistons, don't think that they could use the L34 pistons in the VB-VC.



In 1980 pistons were free as long as they did not increase the compression ratio above 10.5:1 or that specified on the recognition documents, whichever was the higher.


What fuel were they running ?

If they were running pump Super fuel anything over 10.5:1 would of lost power.

Why change let a piston be free like that and come down on a cam chain that had to be single row when they were double sprockets, if I remember correctly Brock and all were totally pissed off about that in the VC Commodore.

If I remember correctly Dickie boy was running a Heavy Duty XE194025 ? Block in the XD-E but for one that blew up the day before the race and he had to use his spare engine with the STD Block, as Dickie boy was saying that he was surprised that that engine lasted so well, also I thought that the VC Commodores were using L34 blocks as well.

I wonder how the cars would of went in stock form like they did back in the pre XA Falcon days when you turned up with street rego driven car, just tweaked with brake pads and a open Carby and dizzy tune and exhaust, engine blue printed and balanced and HD clutch and safety etc not to mention open wheel width spec but street rego tyres should of came into it, as that could of gave people a better idea to chose from, don't think you would of seen anyone running TA's.
As to the way I seen it, I see it from the road driven car point of view that one could buy and do street legal mods to aspect, as that way the race delivers road drivers a better deal to benefit from.
So lets say in 1976-7 what car would I chose 5.8L XC Falcon 4sp or T Bar, 5.0L HX GTS 4sp or T Bar with crap T400 or the LX SS or SL/R500 Torana 4sp or T Bar Trimatic but the weak banjo diff, well I think I would had to wait until March 1977 to get RTS and go for the 5.0L SS Hatch with T Bar and put 14in wheels on it directly and then deal with the engine to up grade that. I would have to wait until Sep 1977 to get a A9X with a good diff. but then the VB 5.0L 4sp came out late 1978 to get a better handling car.

I got The Highlights of Bathurst 1980 to 2002 I have seen to 1986 so far and I am not impressed so much with the information as such is more for the novice. the highlights ? I am more interested in the goings on, the 1973 HQ Holden with the 308 would of been of much interest to me and the 1974 350 HQ was as well, it was not so much only looking at who won, it was everything about the cars and the racing. I do not idolise the drivers I give them credit but it's the cars that are my main interest as any novice can flog on about a driver, sure that's of interest but it does not start or stop with just that aspect, Brock would of never truly won as many races that he did if he did not have the ability to steal a car and calling off the race because of a big smash is BS, because it's not called a 1000km race for nothing in my opinion.
HK1837 Offline
#33 Posted : Thursday, 7 January 2021 10:39:18 AM(UTC)
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There isn’t much after 1969 that were standard road cars. Even in 1969 the works Falcons and the most powerful HDT car were running racing rubber.
I’ve had related to me by someone who had discussions at length with Don Holland about his 1970 XU1, and it was nowhere near standard, was full of HDT tweaks. The Fords would have been no different.
Bruce McPhee’s car in 1968 was standard but gone over by Bruce. Des West’s engine was rebuilt and blueprinted as it was a bit ragged after its first few races, but it was dead stock ex GMH prior to Bathurst other than being tuned to factory specs (this was when Rob Luck tested it, when it was injured from Catalina Park but still did low 15s quarters and did fast 0-100mph times). The three HDRT cars were as supplied by GMH to HDRT other than the race paint applied by GMH and they were fitted with new T0509H5 engines with baffled sumps by GMH. They would have had tweaks for racing though. Bruce’s 1969 GT-HO was similar to his 1968 HK, he basically rebuilt the car to get it perfect, and it paid off for him getting shown the flag for second.
The 1969 HDT HT’s were nowhere near stock, they had hand built Flint and Tonawanda engines (as opposed to engine plant standard) and Lord knows what else Harry did to them. The works GT-HO’s would have been no different.

Edited by user Thursday, 7 January 2021 10:42:26 AM(UTC)  | Reason: Not specified

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8D11PCH2 Offline
#34 Posted : Thursday, 7 January 2021 1:27:12 PM(UTC)
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Originally Posted by: castellan Go to Quoted Post
Originally Posted by: 8D11PCH2 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post


Look at the VB race engine, I have 331hp and the blue VC is 391hp AT 6500RPM with L34 valves and 10.5:1 compression ? how with stock pistons, don't think that they could use the L34 pistons in the VB-VC.



In 1980 pistons were free as long as they did not increase the compression ratio above 10.5:1 or that specified on the recognition documents, whichever was the higher.


What fuel were they running ?

If they were running pump Super fuel anything over 10.5:1 would of lost power.

Why change let a piston be free like that and come down on a cam chain that had to be single row when they were double sprockets, if I remember correctly Brock and all were totally pissed off about that in the VC Commodore.



They had to use pump fuel.

Pistons were free (within the allowed compression ratios) but cam drives (gears, chains, belts) were not. Just the way it was.
As far as I can see cam drives were never free throughout the Group C years.

I do not know whether an engine using 98RON fuel will lose power if the compression ratio is raised above 10.5:1 but I do know the LJ GTR XU1 static compression ratio stated on the recognition documents was 10.3:1 with a tolerance of +/- .5 which means the maximum allowable compression ratio for the LJ XU1 202 engine was 10.8:1
Betcha H.F would have used every last drop of that compression ratio if it was going to give them another 10th of a second.

Edited by user Thursday, 7 January 2021 1:30:51 PM(UTC)  | Reason: Not specified

Dr Terry Offline
#35 Posted : Thursday, 7 January 2021 5:12:10 PM(UTC)
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There also seemed to be a rule change around 1970/71 where the exhaust was made free.

If you look at a lot of the cars especially in 1971 they had the exhaust exiting thru dump pipe under the side sill panel.

Dr Terry

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8D11PCH2 Offline
#36 Posted : Thursday, 7 January 2021 6:08:30 PM(UTC)
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Originally Posted by: Dr Terry Go to Quoted Post
There also seemed to be a rule change around 1970/71 where the exhaust was made free.

If you look at a lot of the cars especially in 1971 they had the exhaust exiting thru dump pipe under the side sill panel.

Dr Terry



Actually 1968 was the 1st year in Group E when exhaust systems were allowed to to be varied after the point of entry into the first muffler, but only if the Supplementary Regulations allowed.

1980 was the 1st year in Group C the complete exhaust system was free.

Edited by user Friday, 8 January 2021 6:47:56 AM(UTC)  | Reason: Not specified

castellan Offline
#37 Posted : Friday, 8 January 2021 9:57:09 AM(UTC)
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Originally Posted by: 8D11PCH2 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post
Originally Posted by: 8D11PCH2 Go to Quoted Post
Originally Posted by: castellan Go to Quoted Post


Look at the VB race engine, I have 331hp and the blue VC is 391hp AT 6500RPM with L34 valves and 10.5:1 compression ? how with stock pistons, don't think that they could use the L34 pistons in the VB-VC.



In 1980 pistons were free as long as they did not increase the compression ratio above 10.5:1 or that specified on the recognition documents, whichever was the higher.


What fuel were they running ?

If they were running pump Super fuel anything over 10.5:1 would of lost power.

Why change let a piston be free like that and come down on a cam chain that had to be single row when they were double sprockets, if I remember correctly Brock and all were totally pissed off about that in the VC Commodore.



They had to use pump fuel.

Pistons were free (within the allowed compression ratios) but cam drives (gears, chains, belts) were not. Just the way it was.
As far as I can see cam drives were never free throughout the Group C years.

I do not know whether an engine using 98RON fuel will lose power if the compression ratio is raised above 10.5:1 but I do know the LJ GTR XU1 static compression ratio stated on the recognition documents was 10.3:1 with a tolerance of +/- .5 which means the maximum allowable compression ratio for the LJ XU1 202 engine was 10.8:1
Betcha H.F would have used every last drop of that compression ratio if it was going to give them another 10th of a second.


Super was 97 octane. with static compression it comes comes to the camshaft design how much more static compression you can use, the later the intake close you need more Static compression as a rule to keep the running compression working within spec due to the volume efficiency, go beyond that and you will get detonation and with to much compression for the fuel octane, then you will have to retard your timing and then you have lost a lot more power.
So there is no advantage of going for to much compression it's just total BS.

I have seen many a street car that was hotted up back in the 70'80's that were built as grenade's, all you heard was compression is the magical key to power, so that's what they got, stupid way to high compression and shit cheap built engine not even fully balanced, shit head work that had been a hack job, wrong carby setup and a 3rd rate tune job.

Look at the Standard leaded petrol octane for example 89 octane I think it was and you could not get away with running a stock HQ 202 9.4:1 high compression on the Standard petrol, you would have to retard your dizzy by say 12 deg to be able to drive it and you would loses that much power and fuel economy that it's just not worth it, same with going to high comp and super you run into the same problem.

If you were to only put a LJ XU-1 camshaft in a stock 9.4:1 202 you could maybe run Standard 89 petrol in it.
The only reason why Holden had to increase the compression in the XU-1 was due to the bigger cam duration, it's running compression would be much the same as the standard 202 had, as all that they did was keep within the values with in regards to the fuel.

So people got the wrong idea back in the 70's by putting stock small chamber 173 heads on a stock 202 thinking that they would have more power, not so ! a mate had a stock HJ 202 with 173 head bought it that way and another mate had a stock 5.8L XC and put 302 heads on it and it was gutless as. they would of been better off just getting a better flowing exhaust and tuned up by a pro.

I find it hard to believe the power of a race VB Commodore 308 with stock heads and stock un touched valves and seats pushing 331hp on 97 octane, they must of used better octane then.

Maybe it all comes from the old Grey motor days that this compression hike was kicked off, as the Grey ran Standard petrol, so if you put super petrol in the old Grey what advantage do you get, nothing ! but shave the head and bring the comp way up to say 9.0:1 or so and you would have created a power house back in the day.
8D11PCH2 Offline
#38 Posted : Friday, 8 January 2021 8:21:35 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
The Camaro was a new 1978 Z28 but CAMS made them run 1974 sheetmetal. It only ran drums early on due to CAMS buggering them around. The Camaro was standard with drums but discs were optional, and in 1981 they ran rear discs.

Whilst the later Z28 weren’t power houses on the road, the engine basics were the same as a 1970 Z28 which was a 370hp engine. It was just pollutioned up and dumbed down for the street and for ULP, but the car was already homologated with good parts under international Group1. Plus KB had been running big horsepower SBC’s in F5000 so they knew the engines well. Given GroupC allowed free choice of certain bits like camshaft, carb etc I’m not surprised the got 480hp. I’d have to search harder but I bet that Group1 homologation included high top pistons, tube headers etc.


Having done some research on KB's Camaro it appears that the CAMS were correct to not allow him to race with disc rear brakes.
Under FIA Recognition to Group 1 GMC never homologated (built 5000 cars with)the J56 disc brake rear end for the Camaro.

RPO J56 - Heavy Duty rear disc brakes were however allowed to be used in FIA Group 2.

The CAMS recognised the Camaro for acceptance into Australian Group C based upon the FIA Group 1 recognition, therefore any parts homologated for use in FIA Group 2 were not allowed to be used in CAMS Group C.
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#39 Posted : Friday, 8 January 2021 8:52:05 PM(UTC)
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I thought J56 was heavy duty brakes? Got you updated front brakes. JL8 was 4 wheel discs. Will look and see what was available on 2nd gen Camaro.
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#40 Posted : Friday, 8 January 2021 9:03:19 PM(UTC)
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FIA Recognition 5310 states RPO J56 Heavy Duty Disc brakes, which gave you disc brake rear axle assy as well as the heavy duty front discs & calipers.
No mention on the recognition documents of JL8 only J56.
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